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I posted this over on the HPTuners forum but thought LStech might get more traffic.
I am looking for some assistance with a tune in my 1971 Corvette LS3 swap. I have the GMPP 525 hp crate motor installed with American Racing Long Tubes and a GTO Vararam intake. The wideband is all over the place after installing the Vararam intake (trying to get cool air to lower my IATs) and I am not sure what needs to be done to correct the issue. The car was tuned by a big local LS tuner but they are so busy I can't get on the schedule any time soon, and even getting in touch with the tuner is almost more work than it is worth. I tried to send the tuner a couple logs so he could tell me what he saw but I can't get a straight answer and really could use some assistance.
The car is currently tuned with MAF only and LTFTs turned off. I am open to any suggestions as this file started from scratch and has had a number of issues getting it all to work... I have tried copying stock LS3 tables, turning on SD/MAF, etc. but the car would barely start, let alone run. Write the file below back to the ECM and it starts up just fine. If I can answer any questions, or provide a different log, please let me know. I am desperate to get this car tuned before next weekend as I have a scheduled track day at Road Atlanta and really planned on taking this car out to have a little fun.
There are two logs attached. The first has the car idling for a while and then a little bit of driving, the second added MAF Hz and is shorter. The tune file is also attached.
Thank you for any help!! I just do not have enough of an understanding to do this stuff and even though I have the tools, I only have a rudimentary knowledge of tuning.
This is what I am working with.
I have attached the logs, but the forum won't let me upload the tune file.
I listed them above, it has the GMPP crate 525 hp motor (ASA cam) with American Racing long tube headers and a Vararam intake. The motor has not been opened or touched internally.
2-1/2" Magnaflow exhaust with X pipe
Jake's performance 4L80e transmission
Speartech Harness & factory ecm from a 2008 Chevrolet express van.
If you do not have EFI they have a demo program that will allow you to view it.
Thanks, I don't have EFILive but believe my laptop has the demo program installed to view files. I guess I can try to copy the erod files over which might get it working in Speed Density with Long-term correction but the MAF table would not be applicable. Also, the e-rod is set to run CATs and probably a bit on the conservative side, I would think? Not sure how well it would work but I am willing to take a look and try to match tables up. I don't know how well EFILive matches up to HPTuners as far as copying the file over, my guess is not very well.
Thanks for the tip though. If anyone else has any advice or something I can provide that would help you help me, let me know!
That short of a tube that close to the throttle body is not the best arrangement for that style MAF and is probably contributing to the problems. At the least you should install a honeycomb air straightener in front of the MAF sensor to see if it helps with the erratic fueling.
That short of a tube that close to the throttle body is not the best arrangement for that style MAF and is probably contributing to the problems. At the least you should install a honeycomb air straightener in front of the MAF sensor to see if it helps with the erratic fueling.
No doubt it isn't ideal. It is either a super short MAF tube, or 170 degree air intake temps. You can see how warm it gets on a 50 degree day at idle even with the Vararam. Only difference is that the old 90 degree bent tube would get even warmer, but then not really cool down when driving. Neither is great for performance but there is no where else to get fresh air in a C3 corvette. The engine bay is TIGHT, and none of the conventional intake tube arrangements work that don't put the filter directly behind the radiator.
I have some Honeycomb inserts from Saxon that I tried back with the old intake tube but they didn't fit the Spectre MAF housing as well so I never pursued keeping it in this configuration. I'll try to find them tomorrow and see if that makes a difference as well.
I installed an air straightener tonight but the weather has been pretty miserable the past few days and is calling for 100% chance of rain tomorrow. Best I'll be able to do is log some idling in the garage until sometime this week.
I didn't have a chance to log anything, but the air straightener, turning on the LTFTs and changing a few DFCO and idle tables based on the EFILive 525 E-Rod motor (and another stock LS3 file) have made the car drive much better.
The rain finally moved through today so I went for a quick cruise. Did a quick (aka shitty) video while I had the car out. It was really windy so I added music that fits my personal taste (my video, my rules) but it does fade out before the end so you can actually hear the car.
Looks like a very nice resto mod, did you do any suspension upgrades? I had a 71 factory LS6 car that is documented, my brother owns it now.
You need to get that WB plumbed into HPT, hopefully you have the pro version & your WB has 1-5v output. Your wasting your time & others by not getting that done.
You can tune the STFT's without the WB for your idle & up to approx. 6000hz. Any WOT without the WB is asking for big trouble, your choice. The WB will make the entire process must quicker, easier & simpler while giving valuable information.
I would suggest starting in MAF only & getting that table dialed, it would be easier for you @ this point.
I'm heading over HPT to see what you have going over there.
Had a look @ the tune, it maybe MAF only already. Do you have a copy of the stock tune?
Looks like a very nice resto mod, did you do any suspension upgrades? I had a 71 factory LS6 car that is documented, my brother owns it now.
You need to get that WB plumbed into HPT, hopefully you have the pro version & your WB has 1-5v output. Your wasting your time & others by not getting that done.
You can tune the STFT's without the WB for your idle & up to approx. 6000hz. Any WOT without the WB is asking for big trouble, your choice. The WB will make the entire process must quicker, easier & simpler while giving valuable information.
I would suggest starting in MAF only & getting that table dialed, it would be easier for you @ this point.
I'm heading over HPT to see what you have going over there.
Had a look @ the tune, it maybe MAF only already. Do you have a copy of the stock tune?
Car has Vette Brakes & Performance full monoleaf suspension with offset trailing arms.
Regarding the tune, there is no stock file. This isn't a GMPP controller so the stock file would be a 2008 Express Van. Regardless, I dropped the car off today with MTI Racing to have the tune cleaned up as I do not have HPTuners Pro and cannot log the WB.
Nice upgrades, bet it drives much better. Did you stay with the solid body frame mounts?
Hopefully MTI will sort out the issue's. I would really suggest upgrading your hardware, you should have a very good base tune to work from. You can spend hours & days perfecting the tune that we cannot afford to pay someone to do. You can still do a lot working with the STFT, cold start is an area you are in OL & no trims a WB is nice. Maybe check & see if they lock the file, you don't want that.
01-02-2015, 08:08 AM
LS3 HPTuners tuning help - 1971 Corvette 
